To celebrate D. Becks' new swimwear line for H&M, obviously!! Remember those steamy H&M swimsuit pics he was featured in just last month? Those glorious looks simply HAD to be celebrated — it was only a matter of time!

Zayn previewed the duet by posting a black and white pic of himself with Swifty on his Instagram -- but hey, she is bestiez with his girlfriend Gigi Hadid, so it wouldn't be unusual that they hang out... But collab?!